Bridging plug



Ost. 30, 1962 T. M. THOMAS, JR

BRIDGING PLUG Filed Nov. 2l, 1958 2 Sheets-Sheet 2 Lmf-m:

States atn Q@ 3,06 l i3 Patented Get. 30, 1962 3,061,013 BRIDGING PLUG Thomas M. Thomas, Jr., Downey, Calif., assigner to Lane-Wells Company, a Division of Dresser Industries, Ine., Houston, Tex., a corporation of Beiaware Filed Nov. 21, 1958, Ser. No. 775,633 3 Claims. (Cl. 1mi- 204) The present invention relates generally to well packing devices and more particularly to bridging plugs and the like apparatus adapted to be set within well bore holes and casings.

Packing devices particularly of the bridging plug type are usually employed for the well-known purpose of closing or sealing o a lower portion of a well bore or to separate upper and lower sections thereof for various purposes. In bridging plugs of the usual type employing a double-ended, resilient packing sleeve body and a pair of sets of oppositely acting casing gripping devices such as serrated slips, it frequently happens that the material of the packing sleeve body will extrude axially toward the casing gripping devices. 'Ihis is most likely to occur where the bridging plug is set in high temperature and/ or high pressure well zones. Such extrusion of the packing sleeve body will usually result in a failure of the seal provided by the bridging plug. It is then necessary to provide another bridging plug at the desired zone. Such replacement is usually time-consuming and expensive and may require that the malfunctioning plug be removed by drilling.

It is accordingly an object of the present invention to provide a bridging plug in which the packing sleeve body will not extrude out of sealing relationship with the well bore.

It is a further object of the present invention to provide a well bridging plug which will have improved holding and sealing capabilities under conditions of high diterential pressures and under conditions of high well temperatures.

A further object of the present invention is to provide a well bridging plug of the aforedescribed nature utilizing well-known construction and operational features of existing bridging plugs and not requiring other than a minimum increase in cost over the cost of conventional bridging plugs.

The objects of the present invention are accomplished in general by interposing a radially expandable metallic ring adjacent the ends of the packing sleeve body, such rings expanding into tight engagement with the well casing when the bridging plug is set so as to restrain extrusion of the packing sleeve material beyond the rings.

These and other objects and advantages of the present invention will become apparent from the following detailed description, when taken in conjunction with the appended drawings wherein:

FIGURE l is a longitudinal sectional View of a preferred form of bridging plug embodying the present invention as the latter appears when assembled ready to be lowered into a Well or when being lowered or suspended within a well casing just prior to setting;

FIGURE 2 is a longitudinal sectional view of said bridging plug in reduced scale showing its appearance and positions of its parts after a setting operation has been initiated;

FIGURE 3 is a longitudinal sectional View of said plug showing its appearance and positions of its parts just after completion of the setting operation;

FIGURE 4 is a longitudinal sectional view of said plug showing its appearance and positions of its parts after the setting operation has been completed and its setting tool has been withdrawn;

FIGURE 5` is a horizontal lsectional view taken on line 5 5 of FIGURE 4; and

FIGURE 6 is a vertically exploded perspective view of one of the expansion ring assemblies of said bridging plug.

Referring to the drawings and particularly FIGURE 1 thereof, a preferred form of bridging plug embodying the present invention includes a centrally located, elongated tubular body or mandrel 10 of substantially uniform external diameter throughout its length and terminating at its lower end in a bull plug 11 of greater diameter. A packing body 12 of resilient material encircles the intermediate portion of the mandrel 10 with its lower end in abutment with a lower packing expander ring 16 and its upper end in abutment with an upper packing expander ring 14. The packing assembly 12 initially has substantial clearance with the walls of the confining enclosure, such as a well casing 20, to insure its unimpeded lowering through the well bore to the desired point at which it is to be set. This is the condition indicated in FIG- URE l. When the bridging plug reaches the portion of the well bore at which it is to be set the packing body is axially compressed between the upper and lower packing expander rings 14 and 16 by suitable means to be fully described hereinafter. This axial compression of the packing body l2 effects its radially outward expansion against the well casing 20, as indicated in FIGURES 2, 3 and 4.

I-t is a particular feature of the present invention that the aforedescribed bridging plug includes upper and lower expansion ring assemblies 22 and 24, respectively, disposed immediately above and immediately below the packing body 12. These expansion ring assemblies are radially expandable from an initial retracted position shown in FIGURE l wherein their outer diameter approximates the outer diameter of the packing body 12 to a radially expanded position shown in FIGURES 2, 3 and 4 wherein their outer peripheries are tightly engaged with the well casing 20. In their expanded position, the expansion ring assemblies 22 and 24 restrain the material of the packing body 12 from extruding beyond the area disposed between these expansion ring assemblies.

More particularly, and with continued reference to FIGURE l, the lower portion of the mandrel 10 is formed with a counterbore 26 of slightly enlarged diameter with this counterbore having internal threads 28. The bull plug 11 is formed with a boss 30 that has external threads 32 received by the threads 28 of counterbore 26. The upper portion of boss 30 is formed with an annular groove 33 wherein is disposed a resilient seal ring, such as an O- ring 34. The bull plug 11 includes an upwardly-facing shoulder 35 which abuts the underside of the mandrel 10. The upper intermediate portion of the external cylindrical surface of the mandrel 10 is formed with a length of downwardly-facing ratchet grooves or buttress threads 36 for a purpose to be described hereinafter. The upper portion of the mandrel 10 is formed with a counterbore 38 of enlarged diameter that receives the lower end of a pull-out sleeve 40. Ihe latter is normally atlxed within the counterbore 3S by a plurality of upper shear screws 42.

A plurality of lower wedge-shaped slips 44 having downwardly-facing serrations or wickets are normally positioned upon the upwardly facing shoulder 35 of the bull plug 11, with their upper portions being positioned about an upwardly diverging lower slip cone 46 that encircles the lower portion of the mandrel 10` and is axially slidably carried thereby. The upper portion of the lower slips 44 are initially affixed to the lower portion of the lower slip cone 46 by a plurality of lower shear screws 48. The lower slips 44 are adapted to undergo radial expansive movement towards the well casing 20 upon downward axial movement of the lower slip cone 46. The upper end of the lower slip cone is formed with an upstanding annular lip S with the lower end of the latter merging into a downwardly and radially outwardly sloping shoulder 52. TheV aforementioned lower expansion ring assembly 24 rests upon the shoulder 52 with its inner periphery encircling the slip cone annular lip 50.

The aforementioned lower packing expander ring 16 rests upon the lower expansion ring assembly 24 and is axially slidably carried by themandrel 1t). The lower -portion of the packing expander ring 16 is formed with a downwardly and radially inwardly tapering shoulder 54 corresponding to the upwardly and radially outwardly tapering upper surface of the lower expansion ring assembly 24. The lower packing expander ring 16 is formed at its radially inner portion with an annular groove 56. A resilient sealing ring, such as an D-ring, SS is disposed within this groove 56 so as to provide a uuid-tight seal between the ring 16 and the external surface of the mandrel 1G at this point.

The lower end of the packing body 12 abuts the upper end of the lower packing expander ring 16. The packing body 12 consists of three separate rings designated 60, 62 and 64, preferably formed of a molded rubber of the synthetic type, such as neoprene, which material is resistant to the solvent effects of petroleum. The upper end of the top packing ring 60 abuts the underside of the upper packing expander ring 14 which ring is axially slidably carried on mandrel 10. The upper expansion ring assembly 22 abuts the upper end of the upper packing expander ring 14. The upper portion of the latter is formed with a downwardly and radially outwardly tapering shoulder 66 corresponding to the upwardly and radially outwardly tapering underside of the upper expansion ring assembly 2.2. A back-up ring 68 abuts the upper end of the upper expansion ring assembly 22, the back-up ring 68 being axially slidably carried by the upper end of the mandrel 10. The lower portion of' the back-up ring 68 is formed with a depending annular ange 70, the outer circumferential surface of which merges into the lower end of a radially outwardly and upwardly extending shoulder 71 whereby the back-up ring 68 complementarily receives the upper portion of the upper expansion ring assembly 22. The upper end of the back-up ring 68 abuts the lower end of an upwardly converging upper slip cone 74, the latter being axially slidably carried upon the pull-out sleeve 40. The upper slip cone 74 is initially fixed against axial lmovement relative to the pull-out sleeve 40 by a shear pin 76. The lower portion of the upper slip cone 74 is formed with a counterbore 78. A split lock ring 80 is disposed within this counterbore 7S. The inner diameter of the locking ring 86 is formed with upwardly-facing buttress shaped grooves or threads 82 adapted to ratchet over and make one-way locking engagement with the downwardly-facing buttress shaped grooves or threads 36 of the mandrel 10. A plurality of wedge-shaped upper slips 84 having upwardly-facing serrations or wickers are positioned upon the upper portion of the upper slip cone 74 with their upper portions encircling the pull-out sleeve 40. The upper slips 84 are initially anixed to the upper slip cone 74 by a pluralityV of top shear screws 86.

The upper surfaces of the upper slips 84 abut the lower end of a tubular ram adapter sleeve S8 forming a part of a conventional setting tool, the details of which are not encompassed within the present invention. The lower portion of the adapter sleeve 88 slidably telescopes over the upper end of the pull-out sleeve 40. The lower tubular strut portion or connector rod 90 of the aforementioned setting tool depends coaxially through the pullout sleeve 40 and into the mandrel 10. The lower end of this connector rod 90 is threadedly connected to the upper end of a rupture stud 92. The lower end of the rupture stud 92 is threadedly connected to the upper end'of boss 30 of the bull plug 11. The rupture stud 92 is provided with a reduced-diameter necked portion 94. The adapter sleeve 8S and the connector rod 90 may essentially resemble the outer sleeve extension of the cylinder and the inner piston parts, respectively, of a setting tool of any suitable type, for example,V as disclosed respectively at 60 and 79 in Forsyth et al. Patent No. 2,566,323, at 1l and 13 in Spangler Patent No. 2,326,404, or at 6 and 16 in Batchelder Patent No. 2,3 82,770.

Referring now particularly to FIGURE 6, there is shown a vertically exploded persepective view of the lower expansion ring assembly 24. It should be understood that the upper expansion ring 22 is substantially identical in construction to the lower expansion ring 24 but that the parts thereof are inverted. Each expansion ring assembly includes vertically stacked lower and upper split rings 190 and 102, respectively. The lower split ring 11H) is formed with an opstanding coaxial annular neck 104 having an inner diameter slightly smaller than the inner `diameter of the upper ring 102 in order that the neck 1514 `may telescopically receive the upper split ring 162. The gaps 106 and 108 of the lower and upper split rings 100 and 102, respectively, should be vertically misaligned, preferably by 18-0 degrees when the rings are assembled, The upper and lower split rings should be formed of a hard, yet iiexible, material, as for example, cast iron, that permits the expansion ring assemblies to undergo radially outward horizontal iiexure without undergoing any change in cross-sectional dimension. As indicated in FIGURE 1, the expansion right assemblies 22 and 24 in their relaxed position have an outer diameter approximating that of the packing body 12. 'Ihe upper yand lower surfaces of the lower expansion ring assembly 24 are iiared radially outwardly so as to be received by the complementarily flared upwardly land downwardly facing surfaces of the lower packing expander ring 16 and the lower slip cone 46, respectively. Similarly, the upper and lower surfaces of the upper expansion ring assembly 22 are flared radially outwardly so as to be received by the complementarily flared upwardly and downwardly facing surfaces of the back-up ring 68 and the upper packing expander ring 14, respectively. Accordingly, when a longitudinal squeezing Aforce is exerted upon the upper and lower expansion ring assembles, they will be wedged radially outwardly and expanded into tight engagement with the walls of the Well casing 20, as indicated in FIGURES 2, 3 and 4.

In the operation of the aforedescribed bridging plug, the plug assembled as shown in FIGURE l is lowered into the well bore upon a suitable setting tool as hereinbefore mentioned to the point at which it is desired to bridge the well. Setting force is then applied to the bridging plug from the setting tool, an upward tension being thereby transmitted .through the connector rod to the bull plug boss 30 and thence as an axial compressive force from the bull plug 11 upward through the bridging plug mandrel 10. This upward compressive force is initially balanced by an equal downward compressive force applied from the setting tool through the adapter sleeve 88, slips S4, shear screws 86, slip cone 74 and shear pin 76. The upward force thus applied to the bridging plug mandrel 10 tends to move the mandrel 10 and pull-out sleeve 40 upwardly with respect to and in opposition to the downward force yfrom the adapter sleeve 88 to a position such as that indicated in FIGURE 2. However, shear pin 76 initially resists such relative motion and opposing forces until the -force reaches a value equal to the shearing strength of the pin. Upon shearing of the pin 76, the opposing forces thus initially applied upwardly through the mandrel 10A and downwardly through the adapter sleeve 88 are suddenly transferred into a longitudinal compressive force acting through the several bridging plug elements on the mandrel between the bull plug shoulder 35 and lower slips 44 and the adapter sleeve 88 and the upper slips 84. This force causes the bottom shear screws 48 to be next sheared. This permits further movement of the adapter sleeve 88 and bull plug 11 toward one another so as to cause the lower slip cone 46 to wedge the lower slips 44 radially outwardly into engagement with the walls of the well casing 20, as indicated in FIGURE 2. 'Ihe beforementioned compressive force acting through the several bridging plug elements lwill also cause the upper and lower expansion ring assembles 22 and 24 to be squeezed radially outwardly and addtionally the packing body 12 will likewise be squeezed longitudinally and thereby expanded radially outwardly against the walls of the well casing 20, as indicated in FIGURE 2. With continued reference to FIGURE 2, it should be noted that during the relative movement of the various parts carried by the mandrel 1), the lock ring Si) will have ratcheted downwardly over the grooves 36 of the mandrel so as to lock the back-up ring 68 against return movement and thereby retain all of the relative downward movement as it takes place.

Referring now to FIGURE 3, continued downward movement of the adapter sleeve 88 relative to upward movement of the bull plug 11 will iinally cause the top shear screws 86 to rupture. The upper slips 84 will then move downwardly relative to the slip cone 74 so as to be wedged thereby radially outwardly against the walls of the well casing 20. Both the upper and lower slips 84 and 44, respectively, will now be in tight gripping engagement with the inside surface of the well casing 26; Additionally, the packing body 12 will be expanded into fluidtight sealing engagement with the inside surface of the well casing. The upper and lower expansion ring assemblies 22 and 24 will likewise be maintained in tight engagement with the inside surface of the well casing. Accordingly, as indicated in FIGURE 3, the upper and lower expansion ring assemblies will serve to positively restain any extrusion of the material of the packing body 12 beyond the point of engagement of the expansion ring assemblies -with the inside surface of the well casing 20.

The mandrel 10, and the parts encircling the mandrel, yare now positively fixed against longitudinal movement relative to the well casing 20. Accordingly, upon continued application of tensile force through the connector rod, the necked portion 94 of the rupture stud 92 will nally fail in tension. The connector rod 90 will then be free to move upwardly. Such upward movement of the connector rod 90 will be directly transferred to the upper wall 120 of the pull-out sleeve 40 by means of an enlarged-diameter threaded portion 122 of the rod. This threaded portion 122 of the connector rod 90 was originally screwed downwardly through complementary internal threads 124 formed on the pull-out sleeves .top wall 120, when the parts of the bridging plug were assembled as shown in FIGURE l. When the upwardly moving connector rod 90 thus exerts suiiicient upward force on top wall 120 of the pull-out sleeve 40, the shear screws 42 will fail and the pull-out sleeve 40 will be free to be withdrawn upwardly from the remainder of the bridging plug, the entire aforementioned setting tool being withdrawn upwardly through the well bore, leaving the bridging plug element set as shown in FIGURE 4. It should be particularly observed that the expansion ring assemblies 22 and 24 are urged into engagement with the walls of the well casing 20 prior to the time that the packing body 12 has undergone complete axial compression and resultant radial expansion into forceful sealing engagement with the borehole wall. This arrangement insures that the ends of the packing body will not be extruded beyond the points of engagement of the expansion ring assemblies and the inside surface of the well casing during the plug setting operation, and this permits the packing body to `be set and maintained at high setting pressure.

With the bridging plug set as shown 4in FIGURE 4, the upper slips 84 securely anchor it in place against upwardly-directed forces produced by fluid pressures below the plug. The lower slips 44 similarly anchor the plug in place against the downwardly-directed forces produced by uid pressures acting downwardly upon the plug. The

expanded packing bodyk 12 will serve to `form a fluid-tight seal within the annulus between the mandrel body 10 and the inside surface of the well casing 20. The bull plug 1-1 blocks fluid flow through the mandrel 10. The material of the packing body will be positively restrained against movement beyond the upper and lower expansion ring assemblies 22 and 24, even where the bridging plug is exposed to high temperature and high pressure conditions. Accordingly, the bridging plug will fulfill its well sealing function until such time as the plug is to be removed from the well bore. The offsetting of the gaps 106 and 108 of the expansion ring assemblies insures that the material of the packing body 12 cannot extrude axially `through the `gaps 108 of the ring elements 102. 4In a bridging plug of the type herein disclosed, substantially all of its principal parts are preferably constructed of materials which are relatively easily drillable by ordinary well drilling tools. This permits removal of the bridging plug if necessary after the plug has been set.

It is to be understood that the foregoing is illustrative only and that the invention is not limited thereby, but may include various modications and changes made by those skilled in the art without departing from the spirit of the invention or the scope of the following claims.

I claim:

l. In a bridging plug that is adapted to be lowered into a well bore, the combination of: a longitudinally extending mandrel; an annular packing body of elastic material encircling said mandrel; upper and lower packing expander rings axially slidably encircling said mandrel adjacent the upper and lower ends respectively of said packing body, the upper portion of said upper expander .ring sloping radially inwardly and upwardly `from its outer periphery and the lower portion of said lower expander ring sloping radially inwardly and downwardly from its outer periphery; upper and lower expansion ring assemblies encircling said mandrel, the upper assembly being disposed above the upper packing expander ring and the lower expansion ring assembly being positioned below the said lower expander ring, each of said assemblies including coaxially stacked upper and lower split rings circumferentially slidable upon one another, with the gaps of said rings being circumferentially olf-set with respect to one another and the upper portion of each said assembly sloping radially inwardly and downwardly `from its outer periphery with the lower portion of each said assembly sloping radially inwardly and upwardly from its outer periphery; a back-up ring axially slidably encircling said mandrel above said upper expansion ring assembly, the lower portion of said back-up ring sloping radially inwardly and downwardly from its outer periphery; a slip cone encircling said mandrel below said lower expansion ring assembly, the upper portion of said slip cone sloping radially inwardly and upwardly from its outer periphery; and means for effecting axial movement of said back-up ring toward said slip cone whereby said split rings will be equeezed radially outwardly against said well bore without undergoing any change in cross-sectional dimension, with said split rings thereby being positioned to directly engage the upper and lower end portions of said packing body so as to restrain the material of said packing body against movement longitudinally beyond said upper and lower expansion ring assemblies.

2. In a bridging plug that is adapted to be lowered into a well bore, the combination o-f: a longitudinally extending mandrel; an annular packing body of elastic material encircling said mandrel; upper and lower packing expander rings axially slidably encircling said mandrel in contact with the upper and lower ends respectively of said packing body, the upper portion of said upper expander ring sloping radially inwardly and upwardly from its outer periphery and lthe lower portion of said lower expander ring sloping radially inwardly and downwardly 7 from its outer periphery; `upper and lower expansion ring assemblies encircling said mandrel, the upper assembly being disposed above the upper ypacking expander ring vand the lower expansion ring 'assembly being positioned below .the lower expander ring, each of said assemblies including coaxially stacked upper and lower split rings circumferentially slidable upon one another with the gaps of said rings being circumferentially oi-set with respect to one another and the upper portion of each said assembly sloping radially inwardly and downwardly from its kouter periphery with the lower portion of each said assembly sloping radially inwardly and upwardly from its outer periphery; a lbaclr-np ring axially slidably encircling said lmandrel above said upper expansion ring assembly, the lower portion of said 4bacloup ring sloping radially inwardly and downwardly 'from its outer periphery; a slip cone encircling said mandrel below said lower eXpansion ring assembly, the upper portion of said slip cone sloping radially inwardly and upwardly from its outer periphery; and means for effecting axial movement of said back-up ring toward said slip cone whereby said split rings will initially be squeezed radially outwardly against 8 the sides of said well bore without -undergoing any change in cross-sectional dimension, whereafter Said packing body will be squeezed radially outwardly against said VWell -bore with said split rings thereby being positioned directly to engage the -upper and lower end portions of said packing body so as to restrain the material of said packing body against longitudinal extrusive movement beyond said upper and lower expansion ring assemblies.

3. Apparatus according to claim 2, and lock means associated with said back-up ring and operative in connection with said mandrel to allow said back-up ring to be moved toward said slip cone as aforesaid but to lock said back-up ring upon said mandrel against retrograde movement.

References Cited in the le of this patent UNITED STATES PATENTS 2,695,068 Baker et al. NOV. 23, 1954 20 2,791,278 Clark May 7, 1957 2,850,101 Johnston et al. Sept. 2, 1958 2,885,009 Baker May 5, 1959 

